A Cross-Linked and Swelling Polymer as an Effective Solid Acid Catalyst

A stable solid acid catalyst, cross-linked poly(ether sulfone) containing high content of sulfonic acid group, was directly synthesized from sulfonic monomer. It was characterized by Fourier transform infrared spectra, thermogravimetric analysis, acid base titration, and reagent uptake. This catalyst exhibited stronger acid strength and a better swelling property than conventional polymer catalyst Amberlyst 15. The effect of swelling on the access to catalytic sites was illuminated. Meanwhile, the cross-linked poly(ether sulfone) catalyst had higher acid concentration, activity, and resistance to solvent than the linear poly(ether sulfone). Acid-catalyzed reactions showed that the cross-linked poly(ether sulfone) catalyst was more active (the turnover frequency of cross-linked poly(ether sulfone) was 5 times greater than that of Amberlyst 15 in esterification of acetic acid and cyclohexanol) and stable than Amberlyst 15 catalyst.